The present invention concerns control systems for crankshaft-milling and -grinding machines of the type provided with a milling carriage movable in a plane which is normal to the longitudinal axis of the crankshaft to be machined. The rotary movement of the workpiece spindle, i.e. its rpm and its angular position, is transformed into longitudinal motion of the milling carriage, the values for speed and position being issued on a digital basis and the operation of the drive for the milling carriage being controlled and regulated by these values by resort to a technique involving an automatic spaced adjustment and position-monitoring and the comparison between commanded and actual values.
With this known type of system, use is made of a mechanical template which serves, in effect, as part of a measuring system for translating the rotary motion of the workpiece into the feed motion of the milling carriage.
The great disadvantage of this arrangement resides in the fact that the production of the template must be performed with the highest degree of accuracy, if the crankshaft ultimately produced is to have the high degree of dimensional exactness required for accurate operation of the cylinders of the combustion machine to be provided with such crankshaft. The accuracy required is down to hundredths of a millimeter.
A further disadvantage of the known system is that the system is tied to the dimensions and configuration of the template employed. Accordingly, when a crankshaft of even minutely different dimensions and/or configuration is to be produced, an entirely new such template must first be prepared. The multitude of different crank web configurations which may be required at different times necessitates considerable expense and inconvenience for keeping in stock a corresponding number of templates and providing an adequate filing system so that a particular template can when needed be located, such template being, quite typically, almost indistinguishable from many other such templates kept in stock.
Lastly, it is necessary that the mechanical part of the feeler device on the template carriage have a radius equal to that of the miller and a breadth equal to the maximum crank throw ever to be implemented.